Dynamic method example in TDPL

[Stanislav Blinov]

  20.08.2010 13:00, Joel Christensen wrote:

There seem to be quite a few errors in this one:

> /**
>     Date: Aug 20, 2010
>     This was copied from TDPL book pages 386 - 387
> */
> module dynamicmethods;
>
> import std.stdio;
> import std.variant;
>
> alias Variant delegate(Dynamic self, Variant[] args...) DynMethod;
>
> class Dynamic {
>     private DynMethod[string] methods;
>     void addMethod(string name, DynMethod m) {
>         methods[name] = m;
>     }
>     void removeMethod(string name) {
>         methods.remove(name);
>     }
>     // Dispatch dynamically on method
>     Variant call(string methodName, Variant[] args...) {
>         return methods[methodName](this, args);
>     }
>     // Provide syntactic sugar with opDispatch
>     Variant opDispatch(string m, /*was: Args*/Args...)(/*was: Args 
> args...*/Args args) { // There should've been variadic template 
> instead of variadic function
>         Variant[] packedArgs = new Variant[args.length];
>         foreach (i, arg; args) {
>             packedArgs[i] = Variant(arg);
>         }
>         return call(m, /*was: args*/packedArgs); // args was used 
> instead of packedArgs
>     }
> }
>
> void main() {
>     auto obj = new Dynamic;
>     obj.addMethod("sayHello",
>         delegate Variant(Dynamic, Variant[]...) { // delegate keyword 
> was missing, and it wasn't matching DynMethod signature
>             writeln("Hello, world!");
>             return Variant();
>         });
>     obj.sayHello(); // Prints "Hello, world!"
> }
Maybe Andrej can add this one to errata too? :)